1. Field of the Invention
The present invention relates to a suspension for a disc drive incorporated in an information processor, such as a personal computer.
2. Description of the Related Art
A hard disc drive (HDD) for writing and reading information to and from rotating magnetic discs has a carriage that is turnable about an axis. The carriage is turned about the axis by a positioning motor. As described in Jpn. Pat. No. 3443021 or U.S. Pat. No. 6,046,883, for example, the carriage has an actuator arm and a suspension on the distal end portion of the arm. The suspension is provided with a base plate, a load beam, a flexure, etc. A head including a slider is disposed on the distal end portion of the suspension. The slider is mounted on a tongue portion of the flexure.
FIGS. 12 and 13 typically show a conventional suspension 1. The suspension 1 comprises a load beam 2 and a slider 4. The slider 4 is mounted on a tongue portion 3 (FIG. 13) of a flexure. When a disc 5 rotates at high speed in the direction of arrow R, air flows between the disc 5 and the slider 4, thereby forming an air bearing 6. An air inflow end and an air outflow end of the slider 4 are referred to as the leading side and the trailing side, respectively, in the art. A dimple 7 is formed near the distal end of the load beam 2. The slider 4 is swingable in a pitch direction and a roll direction around the dimple 7.
As shown in FIG. 13, a read/write element 8 is provided on an end portion of the slider 4 on the trailing side. The distance from the trailing-side end portion of the slider 4 to the disc 5 is called a flying height (FH). A load F produced by a spring force that corresponds to deflection of the suspension 1 acts on the flying slider 4 through the dimple 7. At the same time, a leading-side reaction force P1 and a trailing-side reaction force P2 are produced by an air pressure of the air bearing 6. In order to stabilize the flying characteristics of the slider 4, moreover, a contrivance is made to generate a negative pressure P3.
Due to a mounting error of the suspension 1 on an arm (actuator arm), the mounting height (Z-height in FIG. 12) of the suspension 1 changes inevitably.
In connection with the Z-height position of a suspension, in general, the pitch-direction tilt of the slider with the tongue portion in a free state is called a pitch static attitude (PSA). If the Z-height changes, the PSA also changes. If the Z-height increases, the PSA also increases. If the Z-height is reduced, the PSA is also reduced. If the dimple position is in the center of the slider (central position with respect to the longitudinal direction), the product of the PSA and pitch stiffness represents a pitch moment. The pitch moment influences a flying pitch β (FIG. 13) and also considerably influences the load and the flying height. According to a modern air bearing design of the slider, in particular, flying height sensitivity to the PSA is made higher than to the load, in order to reduce the influence on the flying height of the height above sea level (atmospheric concentration). The shorter an effective length L of the load beam, the more remarkable this influence is.
This is because a load beam 2′ with a shorter effective length L, as compared with the load beam 2 with a longer effective length L, is configured so that an angle α of the load beam changes more sharply as the Z-height changes, as shown in FIG. 12. In the load beam 2′ with the shorter effective length L, therefore, the sensitivity of the PSA to the Z-height is further enhanced, so that it is more difficult to lower the flying height.
According to an investigation conducted by the inventors hereof, the sensitivity of the flying pitch to the Z-height is proportional to the pitch moment that acts on the slider. The higher the stiffness of the flexure, moreover, the higher the sensitivity of the flying pitch β is. In other words, the lower the stiffness of the tongue portion in the pitch direction, the lower the PSA sensitivity around the center of gravity of the slider. In view of the sensitivity of the flying pitch β, therefore, the pitch stiffness of the flexure should preferably be lower.
If the pitch stiffness of the flexure is low, however, the flexure is easily deformed by some external force that acts thereon in its bending direction as the suspension is fixed to the arm (actuator arm) or handled for some purpose.
FIGS. 14 and 15 show prior art suspensions 100 and 101, respectively. In each of the suspensions 100 and 101, limiter members 111 on the distal end portion of a load beam 110 restrain a tongue portion 112 and the like from being displaced for a predetermined amount or more. In the suspension 100 shown in FIG. 14, for example, the limiter members 111 are opposed individually to receiving portions 114 of outrigger portions 113. The limiter members 111 restrain a flexure 115 from being deformed. The limiter members 111 of the suspension 101 shown in FIG. 15 are opposed individually to receiving portions 116 on the opposite sides of the tongue portion 112. The limiter members 111 restrain the flexure 115 from being deformed.
The suspensions 100 and 101 are each provided with trace members 120 that have conductors through which write or read current flows. The trace members 120 are electrically connected to terminals of a slider 121. In order to avoid interference with its corresponding limiter member 111, each trace member 120 is located between the tongue portion 112 and the corresponding outrigger portion 113 along the vicinity of each side portion of the slider 121. The flexure having the trace members 120 of this type is called an inner trace flexure.
The trace members 120 of each of the suspensions 100 and 101 are located between the tongue portion 112 and their corresponding outrigger portions 113. An intensive investigation conducted by the inventors hereof indicates that regions near the terminals of the slider 121 are heated when current (especially, high write current) is supplied to the trace members 120 and the resulting heat may possibly change the PSA and the flying height.